The present invention relates to apparatus for covering a tire bead with an elastomeric material prior to its incorporation into a green tire carcass and the subsequent curing thereof. More particularly the present invention relates to apparatus for applying a supply stock of elastomeric material about the entire circumferential extent of tire beads of any of assorted sizes and shapes. More specifically, the invention relates to adjustable apparatus for precisely applying an elastomeric covering to the entire exterior surface of a tire bead made up of a plurality of wire members irrespective of the diameter and cross-sectional configuration and size of the particular bead.
Over the years, there has been a great proliferation in bead configurations and sizes which have been used extensively in the tire industry. Considering only the standard passenger and truck tire configurations which commonly require covered beads, bead diameters of 14 to 25 inches including numerous intermediate increments have become common in the market. In addition, the width of such beads depending upon the diameter, service and other design characteristics may vary from approximately 0.25 to 1 inch. Another variable in bead design characteristics is that the cross-section of the bead may be square, circular, rectangular, hexagonal, or combinations thereof. The problems presented by the above variables are compounded even further by the fact that some beads are wound with bare wire whereas others are elastomer coated and the specifications of the bead covering material in respect to thickness, flexibility, and tackiness vary substantially between one tire manufacturer and another and even between differing tire sizes and designs.
Since these differing tire sizes and other variables have evolved over a period of many years, it is not surprising that bead covering apparatus has often evolved which is essentially capable of handling only a particular type or limited types of bead configurations which were at the time commonly used in the market or which constituted a new design that was not capable of being handled by existing equipment. Thus, many of the existing bead covering machines are extremely limited with respect to the number of variables in bead design which can be altered while still achieving satisfactory operating and fabrication characteristics.
Further, the prior art bead covering machines have employed a number of significantly differing approaches to the application of cover stock about an annular bead configuration. An early approach to the application of bead covering stock contemplated helical wrapping of a continuous strip of cover material progressively about the annular bead configuration. In order to avoid the complexities inherent in passing a supply spool of the covering stock about the annular bead, a later refinement of this approach contemplated the cutting and spaced helical application of a plurality of strips of cover stock in adjacently overlapping configurations. More recently, the trend has been to the use of a cover stock having a width equivalent to the peripheral distance around a cross-section of a particular bead which is cut to the circumferential dimension of the bead and wrapped therearound. In some instances, one edge of the cover stock is applied to the bead with the remaining width being subsequently sequentially directed into adherence with the bead until the opposite edge abuts or overlies the edge initially applied. Another variation of this approach contemplates the initial attachment of the cover stock to the bead at some laterally medial position with progressively displaced portions in one or both directions laterally therefrom being progressively brought into adhering contact with the bead.
Whichever of the approaches to bead application that has been adopted, the prior art bead covering machines known to applicant have remained relatively complex, have experienced difficulty in achieving uniform covering characteristics upon alteration of the bead variables referred to above, and have otherwise demonstrated a lack of flexibility in regard to providing apparatus capable of adequately handling the requisite number of variables in bead size and design.